[closure-lifetime-fixup] Expose a flag instead of allocating a new instruction.

Small inefficiency I noticed.

Author: gottesmm

include/swift/SIL/SILInstruction.h

@@ -4186,9 +4186,17 @@ class ConvertEscapeToNoEscapeInst final
          SILFunction &F, SILOpenedArchetypesState &OpenedArchetypes,
          bool lifetimeGuaranteed);
 public:
+  /// Return true if we have extended the lifetime of the argument of the
+  /// convert_escape_to_no_escape to be over all uses of the trivial type.
   bool isLifetimeGuaranteed() const {
     return lifetimeGuaranteed;
   }
+
+  /// Mark that we have extended the lifetime of the argument of the
+  /// convert_escape_to_no_escape to be over all uses of the trivial type.
+  ///
+  /// NOTE: This is a one way operation.
+  void setLifetimeGuaranteed() { lifetimeGuaranteed = true; }
 };
 
 /// ThinFunctionToPointerInst - Convert a thin function pointer to a

lib/SILOptimizer/Mandatory/ClosureLifetimeFixup.cpp

@@ -123,12 +123,7 @@ static void extendLifetimeToEndOfFunction(SILFunction &Fn,
   auto OptionalEscapingClosureTy = SILType::getOptionalType(EscapingClosureTy);
   auto loc = RegularLocation::getAutoGeneratedLocation();
 
-  SILBuilderWithScope B(Cvt);
-  auto NewCvt = B.createConvertEscapeToNoEscape(
-      Cvt->getLoc(), Cvt->getOperand(), Cvt->getType(), true);
-  Cvt->replaceAllUsesWith(NewCvt);
-  Cvt->eraseFromParent();
-  Cvt = NewCvt;
+  Cvt->setLifetimeGuaranteed();
 
   // If our Cvt is in the initial block, we do not need to use the SSA updater
   // since we know Cvt can not be in a loop and must dominate all exits
@@ -417,14 +412,7 @@ static bool tryExtendLifetimeToLastUse(
     // Insert a copy at the convert_escape_to_noescape [not_guaranteed] and
     // change the instruction to the guaranteed form.
     auto EscapingClosure = Cvt->getOperand();
-    {
-      SILBuilderWithScope B(Cvt);
-      auto NewCvt = B.createConvertEscapeToNoEscape(
-          Cvt->getLoc(), Cvt->getOperand(), Cvt->getType(), true);
-      Cvt->replaceAllUsesWith(NewCvt);
-      Cvt->eraseFromParent();
-      Cvt = NewCvt;
-    }
+    Cvt->setLifetimeGuaranteed();
 
     SILBuilderWithScope B2(Cvt);
     auto ClosureCopy = B2.createCopyValue(loc, EscapingClosure);
@@ -510,14 +498,7 @@ static bool trySwitchEnumPeephole(ConvertEscapeToNoEscapeInst *Cvt) {
   if (!onlyDestroy)
     return false;
 
-  // Replace the convert_escape_to_noescape instruction.
-  {
-    SILBuilderWithScope B(Cvt);
-    auto NewCvt = B.createConvertEscapeToNoEscape(
-        Cvt->getLoc(), Cvt->getOperand(), Cvt->getType(), true);
-    Cvt->replaceAllUsesWith(NewCvt);
-    Cvt->eraseFromParent();
-  }
+  Cvt->setLifetimeGuaranteed();
 
   // Extend the lifetime.
   SILBuilderWithScope B(SwitchEnum1);